Seven-Coordinate Lanthanide Bis-Halide Bis-Tetrathiometallate Complexes: A Compelling Platform for Luminescent and...

To harness the unique luminescent and magnetic properties of lanthanides, precise control over their coordination sphere is essential, whether to minimize deactivation processes or maximize magnetic anisotropy. The traditional approaches rely on the use of large organic ligands bearing strong atom donors to enforce low coordination numbers of Ln ions. Herein we explored an alternative approach, constraining low coordination numbers via a better control of the primary coordination sphere of the Ln center using fully inorganic sulfur-based ligands, tetrathiotungstates. This strategy led to the preparation of an isostructural series of 13 rare-earth complexes, [NEt₄]₃[LnCl₂(MeCN){(μ-S)₂WS₂}₂] (1Ln, Ln = Ce-Yb and Y). The unusually low coordination numbers (CN = 7) observed here in the absence of sterically bulky or rigid chelating ligands was rationalized using buried volume analysis. We highlight the potential of this new ligand set for luminescent and single-molecule magnets applications by investigating the properties of 1Yb and 1Dy complexes, respectively.